Oxidative degradation and associated mineralization of catechol, hydroquinone and resorcinol catalyzed by birnessite

Abiotic degradation and mineralization of catechol, hydroquinone, and resorcinol catalyzed by birnessite (δ-MnO2) was investigated. Studies were carried out by monitoring changes of pE versus time and pH versus time of the reaction systems during the initial 10 h reaction period and release of CO2 and associated reactions at the end of a 90 h reaction period. The reactions under anoxic condition were compared with aeration condition. The reactions were carried out in suspensions at initial pH of 6.0 under air and N2 atmosphere at room temperature and free of microbial activity. These results indicated that kinetic-related changes of pE versus time and pH versus time were dependent on structural characteristics of phenolic compound and aeration or anoxic condition in the reaction system. The sequence of the mineralization of phenolic compounds catalyzed by δ-MnO2 in presence of air expressed by CO2 release was catechol > hydroquinone ⩾ resorcinol and the differences were significant. However, under an N2 atmosphere the amounts of CO2 released were drastically reduced with insignificant differences among the three reaction systems. Further, phenolic compound degradations, dissolved and adsorbed Mn, and oxidation state of Mn in δ-MnO2 were also determined to elucidate the catalytic efficacy mediated by both O2 and δ-MnO2 in the reaction systems.